1. Field of the Invention
This invention relates to healthcare apparatus and in paroular, though not solely to humidified Positive Airway Pressure (PAP) apparatus used in the treatment of Obstructive Sleep Apnea (OSA) and a method of controlling such apparatus.
2. Description of the Prior Art
OSA is a sleep disorder which affects up to at least 5% of the population in which muscles which normally hold the airway open relax and ultimately collapse, sealing the airway. The sleep pattern of an OSA sufferer is characterised by repeated sequences of snoring, breathing difficulty, lack of breathing, waking with a start and then returning to sleep. Often the sufferer is unaware of this pattern occurring. Sufferers of OSA usually experience daytime drowsiness and irritability due to a lack of good continuous sleep.
In an effort to treat OSA sufferers, a technique known as Continuous Positive Airway Pressure (CPAP) was devised, A CPAP device consists of a gases supply (or blower) with a conduit connected to supply pressurised gases to apatient, usually through a nasal mask. The pressurised air supplied to the patient effectively assists the muscles to keep the patient's airway open, eliminating the typical OSA sleep pattern.
The use of a CPAP system is known to have side effects such as dehydration of the airways and nasal passages which may lead to Rhinitis (inflammation of the nasal passages). The side effects mean that the patient is less likely to comply with his or her CPAP therapy and the therapy itself may cause an increase in meal resistance as a response to the high air flow, degrading the pressure level applied to the airway and thereby reducing the effectiveness of the therapy. Accordingly, a humidified CPAP system would be an improvement. An improvement on the standard CPAP system is described in U.S. Pat. No. 5,537,997 assigned to Respironics Inc. in which a humidifier is incorporated with the CPAP system so that the patient receives humidified gases.
However, a mere combination of a well known humidifier (in which gases are passed through water vapour rising from the surface of water in a water humidification chamber on top of a heaterplate) and a CPAP device would not maximise the benefit of the humidified CPAP therapy to the patient. This is due to the heater plate talig some time to warm up so that the patient would, on some occasions, bc supplied with gases which were not humidified. It should be noted that the sensitive tissues of the nasal passage can be caused to swell after receiving only as little as 10 minutes of non-humidified gases flow. Accordingly, it would be an advantage if the gases received by the patient were always humidified to the capability of the humidifier at any point in time.
Currently, CPAP treatment is delivered via nasal mask. Some patients find a nasal mask claustrophobic and arc therefore unlikely to tolerate the treatment Some OSA sufferers are obligate mouth breathers and unable to tolerate nasal application of gases. A smaller orally attached mouthpiece or mask would be more readily accepted by most patients. In addition, the resistance to gases flow through the nasal passageway is much greater than the resistance to gases flow through the mouth Therefore, the pressure and flow rates of supplied gases could be lowered for orally applied positive airway pressure systems which further means that the breathing attachment could be made lighter and easier to wear.
However, in order to orally deliver gases to a patient, it is very important that the gases are sufficiently humidified at all times. If not, parts of the mouth can dry out within very short times (for example 10 seconds) causing discomfort. In other parts of the mouth salivary glands canbecorne over stimulated causing excess saliva, swallowing difficulties and further discomfort.
It is therefore an object of the present invention to provide breathing assistance apparatus which will at least go some way towards overcoming the above disadvantages or which will at least provide the public with a useful choice.
Accordingly, in a first aspect, the invention consists in breathing assistance apparatus adapted to deliver gases to a patient to assist said patient's breathing comprising:
gases supply means, including pressure regulating means adapted to supply gases at a required pressure level, PA1 gases pressure sensing means to determine the pressure of said supplied gases, PA1 humidification means which receive said supplied gases and humidify said gases, said humidification means capable of variably humidifying said gases up to a reed humidity level, PA1 humidified gases transportation pathway means which channel said humidified gases to said patient, PA1 gases humidity sensing means to determine the humidity of the gases supplied to said patient, PA1 control means which in response to gases humidity and pressure information supplied by said gases pressure and gases humidity sensing moans, controls the pressure of gases supplied by said gases supply means so that the gases flow passing through said humidification means is limited to an amount which can be humidified to said required humidity level by the humidification means at its present humidity level. PA1 i) initiating said gases humidification means to humidify the gases from said gases supply means, PA1 ii) sensing the pressure of said gases, PA1 iii) sensing the humidity of said gases, PA1 iv) deter g a difference pressure value between said predetermined required pressure value and said sensed pressure value, PA1 v) determining a difference humidity value between said predetermined required humidity value and said sensed humidity value, PA1 vi) calculating a required average rate of increase of pressure with respect to humidity by dividing said difference pressure value by said difference humidity value, and PA1 vii) controlling said gases pressure regulating means to increase the pressure of said gases at said required average rate of increase until said predetermined required pressure value is attained. PA1 i) generating a gases flow, PA1 ii) humidifying said gases flow PA1 iii) supplying said gases flow to said patient via said patient's mouth.
In a second aspect, the invention consists in a method of operating breathing assistance apparatus, said breathing assistance apparatus comprising gases supply means, gases pressure regulating means, gases humidification means, humidified gases transportation means and control means storing predetermined required pressure and humidity indication values programmed to carry out the steps of:
In a third aspect the invention consists in a method of treating breathing disorders in a patient comprising tie steps of: